Underfeed stoker



Filed Nov. 27, 1943 E2220 H SMITH I 7 Patented Jan. 8, 1946 UNITED; STAT UNDERFEED STOKER I Eric H. Smith, Worcester, Mass., assignor to Riley Stoker Corporation, Worcester, Mass., a corporation of Massachusetts Application November 27, 1943, Serial No. 511,963

Claims.

This invention relates to underfeed stokers for the burning of fuel, and more particularly to the construction and arrangement of the reciprocable pusher blocks which are used for advancing the fuel along the retorts of such stokers.

An underfeedstoker comprises an elongated trough or retort-into one end of which the fuel is delivered from a hopper by a suitable feeding device, such as a reciprocable ram. Air is discharged into the fuel by means of tuyres located along the upper margins of the retort. One or more reciprocable pusher blocks are provided in the lower portion of the retort for the purpose of moving the fuel along the retort and obtaining a proper distribution of the fuel as it is forced upwardly and laterally over the tuyeres. These pusher blocks as heretofore constructed have been founderratic and undependable in operation in many installations. Particularly when the fuel is wet, or when a thick fuel bed is being maintained, the prior blocks have failed to move the fuel in the proper manner.

It is accordingly the main object of the invention to overcome these difiiculties and to provide an underfeed stoker pusher block construction and arrangement which will operate efficiently even under adverse conditions.

It is a further object of the invention to provide a new and advantageous pusher block adapted for installation in the retort of an underfeed stoker and capable of feeding fuel in a desired manner despite the presence of excessive moisture in the fuel or the maintenance of a thick fuel bed.

With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.

Referring to the drawing illustrating one embodiment of the invention, and in which like referenc numerals indicate like parts,

Fig. 1 is a longitudinal section through an underfeed stoker furnace;

Fig. 2 is an enlarged view in section on the line 2-2 of Fig. 1;

Fig. 3 is a further enlarged plan view of the pusher block; and

Fig. 4 is a section on the line 4-4 of Fig, 3.

The embodiment illustrated comprises a furnace having a front wall I 0, a rear wall I I, and an underfeed stoker retort l2 in th form of an elongated trough extending rearwardly from the front wall. The usual tuyere blocks M are mounted along the upp r margins of the retort to discharge air into the fuel, this air being supplied under pressure to the space beneath the re-'- tort and tuyere blocks in the customar manner by means of a suitable fan (notshown). A fuel hopper I5 is mounted in front of the front "wall l0, and the fuel is delivered from this hopper into the retort by means of the usual reciprocable ram l6 actuated by any suitable means, such as the steam or hydraulic motor IS. A 'slidable pusher rod 19 of well known construction extends along the bottom of the retort l2 and through a guide boss 20 at the rear end thereof. The pusher rod is reciprocated through the medium of the usual lost-motion connection 22 between the ram I 6 and the front end of the pusher rod. i r 1 In order to move the fuel rearwardly along-the retort l2 and cause the fuel to b distributed in a desired manner as it moves upwardly and laterally over the tuyere blocks 14, one or more pusher blocks 25 are secured to the pusher rod [9 within the retort. The number and location of these blocks will depend upon the length of the retort, and in the stoker illustrated I have shown two of them. Each block is formed with a relatively steep rear pushing surface 26 and a gradually sloping front surface 21, as is customary, for the purpose of providing a positive rearward feeding ofthe fuel as the block move rearwardly, and minimizing the tendency of the blocks to drag the fuel forwardly during the return stroke. The pusher blocks are of less width than the retort.

It is found however that with prior stokers the fuel is not always distributed properly, this difficulty being more pronounced when the fuel is wet, or when a heavy fuel bed is being maintained. I have discovered that this difliculty results from the formation'of arches in the fuel within the retort, these arches extending transversely from one side of the retort to the other directly above the pusher blocks. Thus the pusher blocks may operate in a void beneath the arches, with substantially no feeding action on the fuel. In order to prevent such arches from forming, each pusher block is provided with a pair of prongs or horns 29 which extend upwardly from the opposite side portions thereof. These prongs are rigidly connected to th pusher blocks, and they move forwardly and rearwardly along the side walls of the retort. Preferably the prongs flare upwardly and laterally to bring them close to the retort side walls, Since thes side walls are the abutments against which the fuel arches tend to form, the loosening and agitation of the fuel adjacent the side walls by the action of the reciprocating prongs is effective to prevent arch formation. The pusher blocks therefore operate within a solid mass of fuel, which they feed rearwardly in a desired manner. The 'prongs 29 themselves also have some feeding effect, which is enhanced by beveling their front surfaces to a sharp edge ,3!l., thu permitting themto passmore readily; through the fuel astheytravelforwardly. In addition the prongs are inclined upwardly and forwardly so that during their reare ward movement they will impart an upward and The prongsofieacn rearward shove to the fuel. pair are shown integrally connected at their lower ends by a transverse portiongil' thus-$9 10:

to the side walls of the retort to loosen the fuel and prevent the formation of transversearches in the fuel above the pusher block.

viding a substantially U-shaped' structure. This? transverse portion 3| is of considerable width and it is rigidly attached to thetop of the pusher block by means of two cap screws 32.

The operation of the invention will now be apparent: from ma hete disclosure; ram L6 wiile. be recinnocated. bit-the motor d liverin fnelz from-the: hopper l 5.4115110- the tront; portion of I the; retort,- LZ; The mdi. lztkand thenusher' blocks 25;, ith th irsupwardly nr jectngr prongs 2a, will bG -IfQQiDWQB l Q in a direction lengthwiseof the retort rmeans otthe; l st-motionvconnection 22. Thar-pr ngs. 2:9 will-loosen. and i a itate. the .tuel adiacentl t e: smear-walls; at: the retort and; thus pre nt thafonmatiomof transrerse; arches: imthe tuel abovat-thc pushenblockst Thea pusherblncks will accordingly be; efiectivleitoi feedi the fuel: rearwar-db? distribute? tilt? fuelproper1yzas it is forced upwardly" andilaterally.-overz the-1 trnt re mas s; ty a Theiinv ntiomis simp e'illincxpensitz e, and highly eflicient in operation. u

av n thus-r1- described my invention. what I claim. as. new and diHQIQ+SQQfllZ by Letters liat ht i- Y underfeed: stoker comprising; a; trough-r shaped: retort; me ns a. supply fuel: to 5. the: front 9 h tort agrecipr cahla pushe rhlock 1oa ad: n; the. lower nortion of theznetontz toad.- wanca fuelireamardlsi alon the; etonththa'pusher blocighaving a relatively, steep; rear'znushin t-asms I facc and;a1graduallw,slqlzinsfront;surface;means o si mcatet the: rgnshe-r: l sx and pain: of

nrrm s id X' 31 9 6 Withhe; 1 3151 61? lQCk au g ficndi s nmrdl r rs bstand t distance from e RRQ M t deinmfi qnfis hereof; andrclo e 2. An underfeed stoker comprising a troughshaped retort, means to supply fuel to the front end of the retort, a reciprocable pusher block of less width than the retort located in the lower portion thereof to advance fuel rearwardly along theretortuthe pusher block hayin a relatively steep rear pushing surface and a gradually sloping front surface, means to reciprocate the pusher block, and a pair of prongs rigidly connactedlwith the pusher block and extending upwardly for, a substantial distance from the opposite'side; portionsthereof, the prongs flaring upwardlyr and laterally to bring them close to the side walls of the retort to loosen the fuel and prevent the: formation of transverse arches in the fuel above thepusher block.

3". An underfeed stoker comprising a troughshahmil. retort-m ans to supply fuel to-the; front ends of; thercnetort a reciprocahler pusher: block locatedjn the lower portion of the retort; toad,-

vancaiuel rearwardly alongtheretont the pusher block having anrela iively;steep,-v reanpnshing. surfaoeiandiaigraduallyl SIQPlXlgff-IiOIlRSllI-IQMG; means tQr-IQGiPI'zGGfitQ thei 12 161 block and a pair." of sm les rigidly connected. with the pusher. ;block nd x ending: upwardly andzforwardlm for a. sub.-

; stantial, distance fromthe; opposite (side portions aihle widthi connecting thelowencnds: of: the 7 prongs V W a V imrcornsmirfie 

